In general, a session initiation protocol (SIP) is a signaling protocol for identifying each location of terminals to be communicated with each other, and representing procedures for generating, deleting, or changing a multimedia-service session therebetween. The SIP-based service has a request/response structure for controlling generation, correction, and completion of a multimedia-service. The SIP-based service is provided without being dependent on an internet protocol (IP) address by using an SIP URL similar to an E-mail address so as to identify each user.
The SIP-based session service includes a push talk (PT) service. The PT service is for providing communication of a high speed to a service provider and a mobile communication user. The PT service is a semi-double communication service for transmitting media data (talk burst) to one or more clients by one session-set client. The PT service may include one of a PoC (PTT over cellular) service for transmitting audio data, a PTV (push to view) service for transmitting video data, or a PTD (push to data) service for transmitting data.
The PT service allows 1-to-1 communication (a single recipient) or 1-to-many communication (group chat session), and uses an SIP (session initiation protocol) for setting a session.
According to the PT service, one client may invite another client to a PT session according to each client or each group to which the client belongs. That is, if a specific PT client invites one or more PT clients to a PT session by a selection, a session is set therebetween. Accordingly, media data is transmitted to the session-set PT clients.
A PT server may execute a controlling function, or a participating function, or both the controlling function and the participating function.
Each processor for implementing the participating function and the controlling function is called as a participating function unit and a controlling function unit.
The controlling function unit executes a centralized session process, a media distribution, a control for a talk burst including a talker's identity, and provides a policy for participating in a group session and a participant's information, etc. Also, the controlling function unit provides a policy regarding a corresponding session process and a session input, and provides a media relaying function and a talk burst control message-relaying function between the PT client and the controlling function unit.
When n PT clients are session-set to the PT server, the PT server includes n participating function units corresponding to the n PT clients one to one, and one controlling function unit for controlling the PT clients by the participating function units.
When clients participating in a session belong to one or more PT servers, the participating function unit and the controlling function unit may belong to PT servers different from each other.
In case of a chat PT group session and a pre-arranged PT group session, a PT server allocated to a group identity has to execute a controlling function for a PT service of the group. That is, the PT server mapped to the group identity (PT server having the group identity) has to be provided with a controlling function unit thus to be operated as a PT server having a controlling function.
The group identity is an ID of a group. The pre-arranged PT group session is a continuous group session identity consisting of PT members (PT clients). A chatting group is a continuous PT group in which PT clients individually participate for a group session with other PT clients. Accordingly, when the chatting group is session-set, other members (other PT clients) thereof are not necessarily invited thereto. Other members have to individually participate in the chatting group.
FIG. 1 shows a PT system in which a PT server having a controlling function has been determined according to a method for determining a PT server having a controlling function in accordance with the related art. Hereinafter, will be explained an amount of traffics generated when a plurality of clients that belong to different PT servers are session-set in the PT system.
It is assumed that first to third PT clients (11-13) among first to ninth PT clients (11-13, 21-26) belong to a first PT server 10, and fourth to ninth clients (21-26) belong to a second PT server 20. When a PT server having a group identity of the group is the first PT server 10, the first PT server 10 is operated as a PT server having a controlling function of the group. The group identity is an ID of a group. When determining a PT server to have the group identity, a traffic generation amount is not considered. The second PT server 20 executes a participating function.
When the first PT client 11 generates a media traffic, the media traffic is transmitted to the first PT server 10 to which the first PT client 11 belongs through a bearer packet network such as general packet radio service (GPRS). The first PT server 10 having a controlling function generates media traffics corresponding to the number of the second to ninth PT clients (12-13, 21-26) except the first PT client 11 thus to transmit the generated media traffics to the second to ninth PT clients (12-13, 21-26).
That is, the first PT server 10 generates two media traffics for transmission to the second and third PT clients (12-13) that belong thereto, and generates six media traffics for transmission to the second PT sever 20 to which the fourth to ninth PT clients (21-26) belong. The generated six media traffics are transmitted to the second PT server 20 through a GPRS.
The second PT server 20 transmits the media traffics to the six session-set PT clients (21-26).
However, in the related art method for determining a PT server having a controlling function, a PT server having a group ID is determined as a PT server having a controlling function, and an amount of traffics generated from a PT system is not considered. Accordingly, traffics having an unnecessarily excessive amount are generated.